You should report this to UA and to the NJ Dept. of Health ASAP. While it is highly unlikely that this was anything served by UA, there is always that possibility and it's important that UA be able to look at whether there were other passengers on that flight or who ate that batch of food on other flights that day who reported illness. Make sure you provide your whereabouts (and your mother's) for the 2-3 days prior to the flight.

Were you and your mother together at all immediately before boarding the aircraft? Did you snack in a lounge, a restaurant, at home or elsewhere either alone or with her in the 2 days prior?